Google cloud console is the place to go to check for bugs in your application by looking at error logs. Simply click logs under App Engine from left menu in cloud console. Take a look at debug logs for any php errors and also to diagnose any issues.
In your app.yaml file you can define a version name for your app and update it each time you deploy a functioning version of your app. Then from cloud console you can manage versions of your applications. You can publish and unpublish versions of your app with a click of a button. No need to go through any copy paste routines.
When you first signup you are greeted with this screen to get things going. Chose from the many generated funky project ids.
Cloud console instant system wide logs for debugging
Cloud console also allows you to start an Instance. Known as Compute Engine because to allow you to scale your applications Google has separated computing (cpu and ram) from storage (persistent disk, boot disk)
Your application is also in the same neighborhood as Youtube, Maps and many other Google services your app can communicate with and use through APIs.
How to estimate cost of Google Cloud hosting
Use their calculator (https://cloud.google.com/products/calculator/)
How to install software packages on linux vm on Google cloud
On a ubuntu image, you can easily install software on the system by running apt-get. This installs webserver.
sudo apt-get install apache2
This install php5
sudo apt-get install php5 libapache2-mod-php5
If you use centos image you will need to use yum instead of apt-get. This installs apache webserver.
sudo yum install httpd
For CentOS package instructions. Search on the web for package name that are used for apt-get with yum in search term. For example "yum mysql" if you are trying to install mysql. There is no need to install MySQL since google provides much better scalable CloudSql and it's accessible from both your compute engine and App Engine. When you delete an instance your persistent disk and boot disk are saved. Now you can start two or more instances with same boot and persistent disk. All your packages and configurations will be same on all instances.